The Python List is one of the most useful sequences in real-time. A Python list is a sequence of multiple values in an ordered sequence. Unlike Strings, it allows us to store different types of data, such as integer, float, string, etc.
How to declare Python Lists
There are several ways to create a List. The most straightforward way is to place the required items within a square bracket [ ].
How do you create an Empty List?
An object that contains no values or elements is empty, and placing a square bracket creates an empty list in this Python programming language.
ListName = []
How do you create a Python List of Different Data Types?
The first statement is an integer of five integer values or multiple elements within the square brackets. The second statement is a string that contains three String values or three words.
IntegerList = [1, 2, 3, 4, 5]
StringList = [‘apple’, ‘Orange’, ‘Grape’, ‘Mango’]
Python Lists allow placing different data types in a single. It is an example of a mixed, which contains one integer, float, and two integer values.
MixedList = [‘apple’, 2, 3.50, ‘Mango’]
How to access Python List items?
Lists sequentially store data (ordered). So, we can access the elements with the help of indexes. Moreover, using indexes, we can access or alter/change each item present in it separately. The syntax to access Python list items is
ListName([IndexNumber])
The index value starts at 0 and ends at n-1, where n is the size. For example, if the Python list stores 5 elements, the index starts at 0 and ends with 4. To access or alter the first list value, use list_name[0]; to access the fifth list item, use list_name[4]. Let’s see the list example for a better understanding:
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
# Positive Indexing
print(x[0])
print(x[4])
print(x[8])
print('=======\n')
# Negative
print(x[-2])
print(x[-4])
print(x[-8])
Elements output of Positive and Negative Indexes
1
5
9
=======
8
6
2Please use Negative numbers as the index to access the elements from right to left. It means accessing Python list items in reverse order.
x = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']
# Using Positive
print("IP 0 = ", x[0])
print("IP 2 = ", x[2])
print("IP 4 = ", x[4])
print("IP 3 = ", x[3])
print('=======\n')
#Using Negative
print("Pos -1 = ", x[-1])
print("Pos -3 = ", x[-3])
print("Pos -5 = ", x[-5])
print("Pos -6 = ", x[-6])
Accessing elements using both the Positive and Negative Numbers
IP 0 = apple
IP 2 = banana
IP 4 = cherry
IP 3 = orange
=======
Pos -1 = kiwi
Pos -3 = orange
Pos -5 = Mango
Pos -6 = appleAlter List Items
Since there are mutable, apart from accessing items, use these index positions to alter or replace the elements.
Iterate Python List items
A For Loop is the most common way to traverse the items, and it helps to iterate and print the items. This code works accurately to print items inside it. However, to alter the individual element, we need the index position.
To resolve this, we have to use the range function along with Python for loop.
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
for Fruit in Fruits:
print(Fruit)
It multiplies each item by 10. If we want to perform the calculation based on condition, use the If Statement inside the for loop.
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
for Number in range(len(x)):
x[Number] = x[Number] * 10
print(x)
In this example, we declared a String. The first for loop is to iterate and print the items. And the second for loop, along with the range, to iterate each element using the position of an index. Let us see another example.
# Iterate Items
Fruits = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']
# Iterate Elements
for fruit in Fruits:
print(fruit)
# Iterate Items using Index
for i in range(len(Fruits)):
print("Item at ", i, " = ", Fruits[i])
Iterating the String items using for loop and for loop range output
apple
Mango
banana
orange
cherry
kiwi
Item at 0 = apple
Item at 1 = Mango
Item at 2 = banana
Item at 3 = orange
Item at 4 = cherry
Item at 5 = kiwiInsert items into Python List
The available built-in functions to insert new items into the existing one.
- Append(x): The append method adds item x at the end.
- Insert(i, x): The insert method inserts the specified item x at position i.
- Extend(New_List): The extend method adds all the elements in New_List at the end.
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
# Adding items using append
Fruits.append('Blackberry')
print(Fruits)
# inserting items using insert
Fruits.insert(2, 'Kiwi')
print(Fruits)
# Extending using extend
Fruit_new = ['berry','Cherry']
Fruits.extend(Fruit_new)
print(Fruits)
['Apple', 'Orange', 'Grape', 'Banana', 'Blackberry']
['Apple', 'Orange', 'Kiwi', 'Grape', 'Banana', 'Blackberry']
['Apple', 'Orange', 'Kiwi', 'Grape', 'Banana', 'Blackberry', 'berry', 'Cherry']Python List Slicing
In List Slice, the first integer value is the index position where the slicing start and the second integer value is the index position where the slicing end. The Slicing goes until the second integer value but does not include the value at this end index position. For instance, if we specify a [1:4], then slicing starts at index position one and ends at 3 (not 4)
x = [1, 2, 3, 4, 5, 6, 7, 8, 9] # Slicing using two indexes a = x[2:6] print(a) # Slicing using First b = x[:6] print(b) # Slicing using Second c = x[2:] print(c) # Slicing without using two d = x[:] print(d)
[3, 4, 5, 6]
[1, 2, 3, 4, 5, 6]
[3, 4, 5, 6, 7, 8, 9]
[1, 2, 3, 4, 5, 6, 7, 8, 9]Use Negative numbers as the values to slice the elements.
x = [1, 2, 3, 4, 5, 6, 7, 8, 9] # Slicing using Negative first e = x[-3:] print(e) # Slicing using Negative Second f = x[:-2] print(f) # Slicing using Negative first and second g = x[-7:-2] print(g) # Assigning new values x[1:3] = ['t','g'] print(x)
[7, 8, 9]
[1, 2, 3, 4, 5, 6, 7]
[3, 4, 5, 6, 7]
[1, 't', 'g', 4, 5, 6, 7, 8, 9]From the above slicing
- Omitting the first index means the Slicing start from the beginning.
- Omit the second; slicing starts from the first index and continues to the last.
- Use the Negative values to Slice the elements from right to left.
Built-in Functions
In this Python list program, we apply all the built-in methods.
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
x = [9, 4, -5, 0, 22, -1, 2, 14]
#Copying using Copy() Method
New_Fruits = Fruits.copy()
print(New_Fruits)
#Removing all the items using Clear() Method
New_Fruits.clear()
print(New_Fruits)
# Sorting using Sort() Method
Fruits.sort()
x.sort()
print(Fruits)
print(x)
# Reverse using reverse() Method
Fruits.reverse()
x.reverse()
print(Fruits)
print(x)
# position of an item
print('The Index position of Banana = ', Fruits.index('Banana'))
print('The Index position of -1 = ', x.index(-1))
# Counting items using count() Method
y = [9, 4, 1, 4, 9, -1, 2, 4]
print('Number of Times 4 is repeated = ', y.count(4))
print('Number of Times 9 is repeated = ', y.count(9))
['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
[]
['Apple', 'Banana', 'Blackberry', 'Grape', 'Kiwi', 'Orange']
[-5, -1, 0, 2, 4, 9, 14, 22]
['Orange', 'Kiwi', 'Grape', 'Blackberry', 'Banana', 'Apple']
[22, 14, 9, 4, 2, 0, -1, -5]
The Index position of Banana = 4
The Index position of -1 = 6
Number of Times 4 is repeated = 3
Number of Times 9 is repeated = 2sum
The sum function finds the sum of all items.
a = [5, 10, 15, 20, 25]
print(a)
# sum of elements
total = sum(a)
print("\nThe sum = ", total)
[5, 10, 15, 20, 25]
The sum = 75Python List Arithmetic Operations Example
Using the Arithmetic Operators to perform arithmetic operations.
- + operator is concatenating them.
- * operator repeats the element for a given number of times. Here it is three times.
x = [10, 20, 30, 40]
y = [15, 25, 35, 45]
# using + Operator
total = x + y
print("\nAddition : ", total)
# using * Operator
multi = x * 2
print("Multiplication : ", multi)
multi2 = y * 3
print("Multiplication of Y : ", multi2)
Performing arithmetic operations and return output.
Addition : [10, 20, 30, 40, 15, 25, 35, 45]
Multiplication : [10, 20, 30, 40, 10, 20, 30, 40]
Multiplication of Y : [15, 25, 35, 45, 15, 25, 35, 45, 15, 25, 35, 45]